Process for the preparation of fluid bed vinyl acetate catalyst

ABSTRACT

A process for the preparation of a fluid bed vinyl acetate (VAM) catalyst comprising impregnating a support comprising a mixture of substantially inert microspheroidal particles with a solution comprising a metal salt of Pd and M, wherein M comprises Ba, Cd, Au, La, Nb, Ce, Zn, Pb, Ca, Sr, Sb or mixtures thereof, reducing the metal salts to form a deposit of Pd and M on the support surface and impregnating the support with at least one alkali metal salt. At least 50% of the particles used for the microspheroidal support have a particle size below 105 microns.

[0001] This application is a continuation-in-part of U.S. Ser. No.376,180 filed Jan. 20, 1995, which in turn is a continuation-in-part ofU.S. Ser. No. 200,130 filed Feb. 22, 1994.

BACKGROUND OF THE INVENTION

[0002] Field of the Invention

[0003] The present invention relates to a process for producing a fluidbed palladium-promoted catalyst useful in the production of vinylacetate from ethylene, acetic acid and oxygen-containing gas. Inaddition, the present invention relates to a novel fluid bed support andprocess of using the support for the manufacture of palladium-promotedfluid bed catalyst used in the manufacture of vinyl acetate.

[0004] The production of vinyl acetate by reacting ethylene, acetic acidand oxygen together in the gas phase in the presence of a catalyst isknown. Typically, the catalysts are in fixed bed form and supported on aporous carrier material such as silica or alumina.

[0005] Early examples of these catalysts show that palladium and goldare distributed more or less uniformly throughout the carrier (see, forexample, U.S. Pat. Nos. 3,275,680, 3,743,607 and 3,950,400 and GreatBritain Patent No. 1,333,449 and South African Patent No. 687,990).Subsequently, it was recognized that this was a disadvantage since itwas found that the material on the inner part of the carrier did notcontribute to the reaction since the reactants did not significantlydiffuse into the carrier. To overcome this problem, new methods ofcatalyst manufacture were devised with the aim of producing catalyst inwhich the active components were concentrated on the outer-most shell ofthe support. For example, Great Britain Patent No. 1,500,167 claimscatalyst in which at least ninety percent of the palladium and gold isdistributed in that part of the carrier particle which is not more thanthirty percent of the particle radius from the surface. In addition,Great Britain Patent No. 1,283,737 teaches that the degree ofpenetration into the porous carrier can be controlled by pre-treatingthe porous carrier with an alkaline solution of, for example, sodiumcarbonate or sodium hydroxide. Another approach which has been found toproduce particularly active catalyst is described in U.S. Pat. No.4,048,096 and other methods of producing shell-impregnated catalyst aredisclosed in U.S. Pat. Nos. 4,087,622 and 5,185,308. Each of thesepatents is primarily concerned with the manufacture of fixed bedcatalyst useful for the manufacture of vinyl acetate. However, U.S. Pat.No. 3,950,400 also discloses that the catalyst disclosed therein may beused in a fluid bed reactor. In addition, Great Britain Patent No.1,266,623 allegedly discloses a fluid bed catalyst for vinyl acetatemanufacture which comprises palladium promoted with various alkali,alkaline earth or other metals.

[0006] It would be economically beneficial if the manufacture of vinylacetate could be performed in a fluid bed process as well as a fixed bedprocess. Some of the typical benefits from a fluid bed process would bethat the fluid bed reactor design is simpler than a multi-tubular fixedbed reactor, increased catalyst life is to be expected because nodeactivation would take place due to hot spots which are typical of afixed bed reactor, continuous addition of make-up catalyst can maintainpeak performance and virtually eliminate catalyst change-outs, andhigher production rates can be expected because substantially higheroxygen levels may be safely fed into the reactor without producing aflammable mixture.

[0007] Until the discovery of the process of the present invention, thepreparation of palladium-promoted catalyst in fluid bed form has not ledto catalyst having the necessary properties leading to a viableeconomical fluid bed process for the manufacture of vinyl acetate. Theprocess of the present invention overcomes the problems associated withthe prior art resulting in a catalyst giving high performance andadequate attrition resistance so that it may be used in the manufactureof vinyl acetate.

SUMMARY OF THE INVENTION

[0008] It is the primary object of the present invention to provide aprocess for the manufacture of a fluid bed palladium-metal-promotedalkali metal catalyst useful in the manufacture of vinyl acetate.

[0009] It is another object of the present invention to provide a novelsupport for use in the production of a fluid bedpalladium-metal-alkali-metal-promoted catalyst useful in the fluid bedmanufacture of vinyl acetate.

[0010] It is still another object of the present invention to provide anovel process for the production of a support useful in the manufactureof vinyl acetate catalyst.

[0011] Additional objects and advantages of the invention will be setforth in part in the description which follows and, in part, will beobvious from the description or may be learned by practice of theinvention. The objects and advantages of the invention may be realizedand attained by means of the instrumentalities and combinationsparticularly pointed out in the appended claims.

[0012] To achieve the foregoing objects of the present invention, theprocess of manufacturing a fluid bed vinyl acetate catalystcharacterized by the following formula comprising Pd-M-A wherein Mequals barium, cadmium, gold, lanthanum, niobium, cerium, zinc, lead,calcium, strontium, antimony, or mixtures thereof; and A equals at leastone alkali metal or mixture thereof comprises impregnating a pre-formedmicrospheroidal support wherein at least 50% of the particles have aparticle size diameter selected to be below 105 microns with a solutioncomprising a metal salt of the palladium, M and at least one alkalimetal and drying the impregnated catalyst. The substantially inertparticulate support typically comprises microspheroidal particlesselected from the group consisting of alumina, silica, titania,zirconia, and/or mixtures thereof.

[0013] In another embodiment of the present invention the process isperformed using an aqueous solution free or substantially free of anyorganic solvent.

[0014] In a preferred embodiment of the present invention the metal saltof the alkali metal is separately impregnated onto the support,preferably subsequent to the impregnation of the solution comprising thesalts of palladium and M element onto the support material.

[0015] In another embodiment of the present invention, the impregnatedsupport may be subjected to known reduction procedures (e.g., heatingunder reducing conditions) to form a deposit of palladium and M on thesurface of the support. The reduction can take place either before orafter the deposition of the alkali metal solution.

[0016] In a still further preferred embodiment of the present inventionthe catalyst is dried at a temperature below 80° C., preferably betweenabout 60° to 70° C.

[0017] In another preferred embodiment of the present invention theparticle size (particle diameter) of the substantially inert supportmaterial is selected such that at least 50% of the particles are belowabout 105 microns. Preferably, at least 75% of the particles are below105 microns, especially preferred being at least 85% below 105 microns.Finally the preferred support is substantially free of sodium.

[0018] In another embodiment of the present invention, the support forthe manufacture of the vinyl acetate catalyst comprises a mixture ofsubstantially inert microspheroidal particles having a pore volume ofbetween 0.2 to 0.7 cc/g and/or a surface area of between 50 to 200 m²/gand at least 50% of said particle are less than 105 microns.

[0019] In a preferred aspect of this embodiment of the presentinvention, at least 75% of the particles are below 105 microns,especially preferred being at least 85% below 105 microns.

[0020] In another embodiment of the present invention, the support forthe manufacture of the vinyl acetate catalyst comprises microspheroidalinert particles, preferably silica, zirconia, alumina, titania ormixtures thereof wherein said particles have a pore volume of between0.2 to 0.7 cc/g and/or a surface area of between 50 to 200 m²/g and areobtained from a mixture of less than 100% to 20% inert support sol andgreater than zero percent to 80% dried inert particles.

[0021] In a preferred embodiment of this aspect of the presentinvention, the pore volume of the inert particles is between 0.3 to 0.65cc/g, especially preferred being 0.4 cc to 0.55 cc/g.

[0022] In a further preferred embodiment of this aspect of the presentinvention, the surface area is between 50 to 150 m²/g, especiallypreferred being 60 to 125 m²/g.

[0023] In a further aspect of this embodiment of the present invention,the silica microspheroidal support material is manufactured by mixingbetween 20% to less than 100% silica sol with 80% to greater than zeropercent silica such as Aerosil®, spray drying said mixture at anelevated temperature of between 115° to 280° C., preferably 130° to 240°C., and calcining said spray dried particles preferably at a temperatureof between 550° to 700° C., preferably between 630° to 660° to form thesupport material.

[0024] Typically, the weight percent of the palladium, M and alkaline inthe catalyst of the present invention are: 0.1 to 5.0 wt % palladium,preferably 0.2 to 4.0 wt %; greater than 0 to 10 wt % alkali metal,preferably 0.1 to 8.0 wt %, most preferably 0.1 to 5.0 wt %; greaterthan 0 to about 5.0 wt % M, preferably 0.1 to about 4.0 wt %.

[0025] The catalysts of the present invention may be used in a fluid bedreactor for the reaction of ethylene with oxygen to produce vinylacetate. The reaction temperature is suitably 100° to 250° C.,preferably 135° to 190° C. The reaction pressure is suitably 50 to 200psig, preferably 75 to 150 psig.

DETAILED DESCRIPTION OF THE INVENTION

[0026] Reference will now be made in detail to the present preferredembodiment of the invention of which the following examples are setforth for illustrative purposes only.

[0027] Reactor Testing For Examples 1 to 20

[0028] The catalysts were tested in a bench scale fluid bed reactor witha maximum catalyst capacity of 40 cc. Thirty cc of catalyst orcatalyst-plus-diluent was the typical volume of solid loaded into thereactor. In general, sufficient catalyst was used such that the reactorcontained 0.093 g of palladium metal with each catalyst evaluation. Atotal of 30 cc volume was obtained by mixing sufficient inertmicrospheroidal silica with the active catalyst prior to reactortesting. The reactor was equipped with two feed inlets. For some of theexperiments of this study, ethylene, acetic acid, and oxygen all enteredthe reactor through the lower inlet and nitrogen only was fed throughthe central inlet. In other tests, additional oxygen was fed through thecentral feed inlet. This central inlet was located 2.5″ above the lowerfeed inlet.

[0029] The reactor pressure was controlled at 115 psig and all linesleading to and from the reactor were heat traced and maintained at 150°to 155° C. order to prevent condensation of liquid feeds or products.Typical temperatures for the fluid bed reactor can vary from 100° to250° C., preferably 135° to 190° C.

[0030] The gaseous reactor effluent was analyzed on-line using a HewlettPackard Model 5890 gas chromatograph equipped with both TCD and FIDdetectors. Oxygen, nitrogen, ethylene and carbon dioxide were separatedon a 13x mole sieve column parallel with 10% carbowax 20M on 80/100Chromosorb WAW and 23% SP2700 on 80/100 Chromosorb PAW, and quantitatedwith the TCD. Vinyl acetate and acetic acid were separated on a 4%carbowax 20M on 80/120 carbopack column and quantitated with the FID.

[0031] Support Preparation

[0032] Two types of preformed microspheroidal silica were prepared andutilized as supports in the practice of the present invention. Prior touse, all supports were sieved and a specific particle size distributionof the support was used in all catalyst preparations:

[0033] 5% of the particles are less than 105 microns but greater than 88microns

[0034] 70% of the particles are less than 88 microns but greater than 44microns

[0035] 25% of the particles are less than 44 microns

[0036] It should be understood the particle size distribution recitedabove is not intended to be limiting and that variations in thisdistribution are contemplated depending upon reactor size and operatingconditions.

[0037] Support 1

[0038] Support 1 was prepared by spray drying a mixture of Nalco (NalcoChemical Company) silica sol 1060 and DeGussa Aerosil® (DeGussa ChemicalCompany) silica. In the dried support, 80% of the silica came from thesol and 20% of the silica came from the Aerosil®. The spray driedmicrospheres were calcined in air at 640° C. for 4 hours.

[0039] Aerosil® silica is the trade name of Degussa's fumed silica. Thismaterial has high surface area (˜200 m²/g), essentially no micropores,uniform particle size distribution in the nm-range (1×10⁻⁹ meter), andis free of sodium. Fumed silica having properties comparable to Aerosil®may be produced by other companies and may be used in the place ofAerosil® in the preparation of Support 1.

[0040] Nalco silica sol 1060 is particularly advantageous for use in ourapplication because of large mean particle size of the silica particlesin the sol, 60 millimicrons. These larger silica particles pack lessefficiently than smaller sol particles (˜30 millimicrons as in Nalco2327) and yield a final support higher in pore volume in the mesoporeregion and lower in micropore volume. Other silica sols which have asimilarly large (˜40 to 80 millimicrons) mean particle size of thesilica may be utilized in the place of the 1060 silica sol in thepreparation of Support 1.

[0041] Support 2

[0042] A series of microspheroidal supports (Supports 2A-2D) containingKA-160 (Sud Chemie) were prepared as follows:

Support 2A: 75% SiO₂ from KA-160 with 25% SiO₂ from Sol

[0043] 750 g of KA-160 was ground to pass through a 35 mesh screen andwashed to remove any soluble impurities, such as chloride ions. Thissolid silica was then mixed with 694.4 g of Snotex-N-30 (NissanChemical) (36 wt % solids) silica sol and 556 g distilled water. Thismixture was milled overnight in a jar mill. The smooth slurry was thenspray dried to form microspheroidal particles suitable for use in afluid bed reactor. The microspheroidal support was then calcined at 640°C. in air for 4 hours.

[0044] The role of the KA-160 support is to provide much of the porestructure within the microspheroidal particle. The fixed bed support,KA-160, is produced by Sud Chemie and has properties which areadvantageous for use in vinyl acetate catalyst preparation. Moderatesurface area (160 m²/g), little or no microporosity, and substantialporosity (˜0.57 cc/g) in the mesopore region are advantageous propertiesof KA-160. Alternative fixed bed catalyst supports are available withsurface area and pore volume properties similar to KA-160 (little or nomicropores, mesopore volume of ˜1.5-0.25 cc/g, and surface area 80-200m²/g). These supports may be utilized in the place of KA-160 in thepreparation of Support 2.

Support 2B: 65% SiO₂ from KA-160 with 35% SiO₂ from Sol

[0045] This support was prepared in the same manner as Support 2A exceptthat 227.5 g of KA-160, 408.3 g of Snotex-N-30 (30 wt % solids) and 64 gof distilled water were used.

Support 2C: 50% SiO₂ from KA-160 with 50% SiO₂ from Sol

[0046] This support was prepared in the same manner as Support 2A exceptthat 175 g of KA-160 and 583.3 g of Snotex-N-30 (30 wt % solids) wereused.

Support 2D: 75% SiO₂ from KA-160 with 25% SiO₂ from Sol

[0047] This support was prepared in the same manner as Support 2A exceptthat 262 g of KA-160, 219 g of Nalco 2327 (40 wt % solids) (NalcoChemicals Company) and 219 g of distilled water were used.

[0048] Each type of microspheroidal silicas prepared above may be usedadvantageously in the preparation of fluid bed vinyl acetate monomercatalyst according to the process of the present invention. For use inthe manufacture of fluid bed catalysts via impregnation with activemetals, these supports provided unexpected superior physical propertiesfor the vinyl acetate catalysts of the present invention compared to anyreadily available supports. Selected analytical data on all supports areincluded in Table 1 below. TABLE 1 PHYSICAL PROPERTIES OF CUSTOMIZEDMICROSPHEROIDAL SILICA SUPPORTS Wt % Sol- ids Pore Tot Ap Attrition inVol r ≦ Pore Bulk Calcin Resist Slur- 4,500 A Vol Density SA Time/ LossSupport ry (cc/g) (cc/g) (g/cc) m²/g Temp 0-20 hrs Support 1 62 0.390.46 0.78 124.4 4 hr/ <5% 640° C. Support 50 0.60 0.60 0.65 175.5 4 hr/0.33% 2A 640° C. Support 50 0.39 0.39 0.72 184.4 4 hr/ 0.35% 2B 640° C.Support 46 0.27 0.33 0.77 191.9 4 hr/ 1.65% 2C 640° C. Support 50 0.620.63 0.60 156.0 4 hr/ 2D 640° C.

[0049] Catalyst Preparation

[0050] The general method utilized in the preparation is summarizedbelow.

[0051] Typically, the microspheroidal support is impregnated with asolution (or solutions) of the active metals using the incipient wetnesstechnique. Compounds of the active metals, palladium, M element (e.g.gold) and potassium acetate, may be dissolved in the appropriate ratiosin a suitable solvent, then impregnated upon the microspheroidalsupport. In general, it is desirable if all of the active metals to beused in a catalyst preparation are dissolved in a single portion ofsolvent which is of the volume just adequate to fill the pore volume ofthe support. In some instances a desired promoter may not be soluble inthe same solvent as the other metal compounds to be used. In this case asolution containing some of the metal components may be impregnated uponthe support, followed by impregnating a second solution containing theremaining components. Solvents which are useful include water andvolatile organic solvents such as: carboxylic acids with four carbons orless, alcohols, ethers, esters, and aromatics. After the wet catalyst isdried, it may be used for the production of vinyl acetate or it mayfirst be reduced by means known to those skilled in the art.

[0052] In general, when acetic acid is present and the catalyst isheated at an elevated temperature (˜100° C.) the catalyst darkens toblack and becomes inactive. Additionally, when a solution of palladiumacetate (with or without other metal acetates) is heated to too high atemperature or for too long, the solution changes color from theoriginal red-orange to a greenish color and a black precipitate forms.In general, 60° C. is a safe temperature to work at, but up to ˜80° C.has been used for brief periods of time, to dissolve the palladiumacetate.

EXAMPLE 1

[0053] A catalyst having the following composition 0.75 wt % Pd, 0.32 wt% Au and 2.88 wt % K was prepared by dissolving palladium acetate in anacetic acid solution of the gold acetate reagent described in U.S. Pat.No. 4,933,204 and impregnating this combined solution upon a preformedmicrospheroidal Support 2A identified above. The solid was dried at 60°C. using a rotary evaporator (rotovap), then the Pd and Au were reducedwith an aqueous solution of hydrazine (no alkali hydroxide). The solidwas washed to remove hydrazine, dried and potassium acetate wasimpregnated upon the solid. A 12.67 g (16.7 cc) charge of catalyst wasplaced in the reactor for testing. The results of reactor testing ofthis catalyst at various conditions are set forth below in Table 2.These results show an 18.2% conversion with 83% selectivity using 10.55O₂, 14.31% HOAc, at 164.9° C.

EXAMPLE 2

[0054] The catalyst of this example had a composition of 1.07 wt % Pd,0.40 wt % Au and 2.89 wt % K and was prepared according to the procedureset forth in Great Britain Patent 1,266,623 except that the support wasthe same as used in Example 1. A 8.68 g (11.3 cc) charge of catalyst wasplaced in the reactor for testing. The results of testing of thiscatalyst at various conditions is set forth below in Table 2 and gave8.1% ethylene conversion and 84.4% vinyl acetate selectivity using 7%O₂, 10% HOAc, at 159° C.

EXAMPLE 3

[0055] The procedure of Example 2 was repeated to produce a catalysthaving a composition as follows: 1.01 wt % Pd, 0.38 wt % Au and 2.60 wt% K. However, Support 1 identified above was utilized. A 9.2 g (10.6 cc)charge of catalyst was placed in the reactor for testing. The reactortesting at various conditions is set forth below in Table 2. Thecatalyst gave C₂H₄ conversion of 8.6 and VA selectivity of 85.3 underthe same conditions as set forth in Example 2.

[0056] The performance of the catalyst of Examples 2 and 3 is verysimilar but the catalyst prepared on the Support 1 appears to beslightly more active. As the compositions of these two catalysts arenearly identical, the difference in activity may be due to the differentsupports.

EXAMPLE 4

[0057] This catalyst was prepared according to the teachings of U.S.Pat. No. 3,950,400 except that microspheroidal (fluid bed) Support 1 asdescribed above was utilized. The composition was 0.82 wt % Pd, 0.40 wt% Au, 0.13 wt % Ba, 2.69 wt % K. The acetic acid was carefully removedunder vacuum (using a rotary evaporator) at 60° C. This solid remainedtan in color. A 11.57 g (13.4 cc) charge of catalyst was placed in thereactor for testing. Reactor testing of this catalyst set forth in Table2 demonstrated it to be highly active and selective. At 164° C. using 7%oxygen and 14% acetic acid, 12.5% ethylene conversion was obtained with87.2% selectivity.

EXAMPLE 5

[0058] A catalyst having the following composition: Pd 0.81 wt %, 0.34wt % Au and 2.71 wt % K was prepared by dissolving palladium acetate(PdAc) and potassium acetate (KAc) in acetic acid, then adding goldacetate and impregnating it on Support 1. The acetic acid was removedunder vacuum, at 60° C. This solid was tan in color at this point. Thepreparation of this catalyst is similar to that of Example 1 exceptthere was no catalyst reduction prior to testing. A 11.75 g (13.2 cc)charge of catalyst was placed in the reactor for testing. The results oftesting this catalyst under various conditions is set forth in Table 2.The catalyst gave 9.2% conversion with 87.8% VA selectivity.

EXAMPLE 6

[0059] A catalyst having the following composition: 0.77 wt % Pd, 0.40wt % Au and 2.2 wt % K was prepared as with Example 5. The solid wasthen subjected to a hydrazine reduction, washed with water to removehydrazine, and additional potassium acetate was added. A 14.25 g (17.6cc) charge of catalyst was placed in the reactor for testing. Excellentreactor results were obtained as shown in Table 2. This catalyst gavesimilar results, 10.17% conversion with 85.7% selectivity, as comparedwith Example 5.

[0060] A variety of Pd/M/K on silica-type catalysts were preparedwherein M is not gold. Metals evaluated included M=Ba, La, Sb, Pb, Ce,Nb, Ca, Zn, and Sr. The following examples are illustrative of thesevarious metals.

EXAMPLE 7

[0061] The catalyst was prepared with the lower level of palladium whichis typically used with Bayer-type catalysts, 0.88 wt % Pd, but which istypically too inactive for use with Hoechst-type catalysts along with0.88 wt % Ba. Acetic acid was the solvent. The catalyst had 2.9 wt % K.A 15.52 g (21.0 cc) charge of catalyst was placed in the reactor fortesting. The results of testing conversions approaching 10% ethylenewith 81% selectivity to VA were obtained under various conditions as setforth below in Table 2. The catalyst suffered some deactivation byexposure to an elevated temperature (100° C.) while acetic acid wasstill present.

EXAMPLE 8

[0062] A catalyst having 0.41 wt % Pd, 0.49 wt % Ba and 2.2 wt % K wasprepared using water as the sole solvent. The mixture of palladiumacetate, potassium acetate and barium acetate is sufficiently soluble indistilled water that water can be used as the sole solvent. A 24.77 g(30.0 cc) charge of catalyst was placed in the reactor for testing.Reactor testing of this catalyst under various conditions is set forthbelow in Table 2 and gave 10% ethylene conversion at 85% selectivity toVAM.

[0063] The use of water as the impregnating solvent instead of aceticacid has several significant advantages. Water is certainly lessexpensive, less toxic and less corrosive than acetic acid. All of whichwill give a less expensive process using water. Additionally, water doesnot act as a reducing agent for the palladium. When heated at 100° C. inthe oven, the catalyst prepared with acetic acid darkened to near black,whereas the analogous catalyst prepared in water, retained its tan colorand still retained its excellent reactor performance. Finally, waterwould be a more benign solvent with respect to any detrimental effectsupon the support.

EXAMPLE 9

[0064] A solution of palladium acetate, potassium acetate and antimonyacetate in acetic acid were impregnated upon the preformedmicrospheroidal support. The wet solid was dried at 60° C. under vacuum.No pre-reduction of the catalyst was performed. The resulting catalystcomprised 0.81 wt % Pd, 0.70 wt % Sb and 2.9 wt % K. A 10.95 g (12.8 cc)charge of catalyst was placed in the reactor for testing. Reactortesting shown in Table 2 gave ethylene conversions of nearly 17% with89% selectivity at only 9 mole % oxygen in the feed mixture.

EXAMPLE 10

[0065] The addition of barium to an antimony containing catalystsubstantially reduced catalyst activity. The catalyst tested had acomposition (wt %) of 0.71 Pd, 0.71 Ba, 0.71 Sb and 2.6 K. A 10.95 g(13.5 cc) charge of catalyst was placed in the reactor for testing.There is no synergy between the antimony and the barium at the levelsevaluated as shown by the results in Table 2 below.

EXAMPLES 11 and 12

[0066] A mixture of palladium acetate, lanthanum acetate and potassiumacetate was quite soluble in acetic acid. Support 1 was used for Example11 and Support 2A for Example 12. This solution impregnated upon thepreformed support and dried under vacuum resulted in an excellentcatalyst as shown in Table 2 below. The composition of catalysts 11 and12, respectively, in weight percent were as follows: 0.77 Pd, 0.70 La,2.7 K; 0.80 Pd, 0.57 La, 3.1 K. For Example 11, a 10.95 g (13.0 cc)charge of catalyst was placed in the reactor for testing. For Example12, a 10.95 g (15.0 cc) charge of catalyst was placed in the reactor fortesting. Conversions and selectivities were slightly lower than with theantimony-containing catalyst, but were still very good.

EXAMPLE 13

[0067] The mixture of palladium acetate, lanthanum acetate and potassiumacetate was dissolved in water instead of acetic acid resulting in acatalyst having the following composition: 0.15 wt % Pd, 0.34 wt % La,1.4 wt % K. A 25.2 g (30.0 cc) charge of catalyst was placed in thereactor for testing. Considering the low level of palladium present, theethylene conversion of 8% as shown in Table 2 was quite good.

EXAMPLE 14

[0068] Niobium oxalate, the source of niobium utilized, was insoluble inacetic acid. For that reason the niobium oxalate was pre-impregnatedonto Support 1 using an aqueous solution. After drying the support, anacetic acid solution of palladium acetate and potassium acetate wasimpregnated upon the support. A 11.04 g (14.0 cc) charge of catalyst wasplaced in the reactor for testing. Resulting catalyst composition was0.81 wt % Pd, 0.64 wt % Nb, 3.1 wt % K. Reactor performance was adequateat ˜9% conversion and 84% selectivity, but this catalyst appeared todeactivate more rapidly than expected.

EXAMPLES 15 and 16

[0069] Calcium was added as the promoter at two different levels: (1)the same mole % as barium in Example 7, and (2) at near the wt % levelas barium in Example 7. In each case, Support 2A was used. For Example15 a 10.95 g (15.8 cc) charge of catalyst was placed in the reactor fortesting. For Example 16, a 10.95 g (15.4 cc) charge of catalyst wasplaced in the reactor for testing. Neither catalyst performed well asshown in Table 2, but the lower level of calcium gave higher conversionsand higher selectivities. It is possible that adjusting the calciumlevel further could improve catalyst performance.

EXAMPLES 17 and 18

[0070] Cerium promoted catalyst (Example 17) and zinc promoted catalyst(Example 18) were prepared as described in the general procedure setforth above with the metals being dissolved in acetic acid and drying at60° C. under vacuum. In each case, Support 2A was utilized. The finalcomposition of the catalyst were: Example 17—0.80 wt % Pd, 0.69 wt % Ce,2.8 wt % K; Example 18—0.81 wt % Pd, 0.33 wt % Zn and 2.9 wt % K. A10.96 g (15.6 cc) charge of catalyst was placed in the reactor fortesting for Example 17. For Example 18, a 10.96 g (15.6 cc) charge wasused. Tests of these catalysts showed potential as shown in Table 2.Optimization of promoter level and reduction treatment could bebeneficial. In particular, cerium showed very good initial activity.

EXAMPLES 19 and 20

[0071] The catalyst of Examples 19 and 20 were prepared on the samesupport and utilizing substantially the same procedure set forth inExamples 17 and 18 above except that Pb and Sr were substituted for Ceand Zn. The final composition of Example 19 on a wt % basis was 0.81 Pd,0.70 Pb, 2.9 K. The final composition of Example 20 on a wt % basis was0.80 Pd, 0.68 Sr, 2.7 K. For Example 19 a 11.71 g (13.2 cc) charge ofcatalyst was placed in the reactor for testing. In Example 20 a 10.95 g(15.4 cc) charge was used. As shown in Table 2, the lead promotedcatalyst appeared to deactivate more rapidly than expected, while thestrontium promoted catalyst was of low activity and poor selectivity.TABLE 2 RUN DATA SUMMARY — FLUID BED VAM IMPREGNATED CATALYSTS % C2H4 %VA BED T TOTAL FEED COMPOSITON Run # CONV SEL (C) FLOW O2 N2 C2H4 HOACPsig HRS Example 1 1 14.42 85.38 163.0 396.41 7.040 30.65 47.930 14.380115 0.8 2 14.87 87.16 161.5 396.41 7.040 30.65 47.930 14.380 115 2.4 314.46 86.00 161.9 396.41 7.040 30.65 47.930 14.380 115 2.9 4 18.20 83.06164.9 396.41 10.550 27.17 47.970 14.310 115 3.9 5 17.95 86.86 161.7418.63 10.010 31.17 45.390 13.430 115 6.0 6 17.38 88.86 155.5 418.6310.010 31.17 45.390 13.430 115 6.3 7 17.57 87.80 158.2 418.63 10.01031.17 45.390 13.430 115 6.9 8 17.01 88.05 157.2 418.63 10.010 31.1745.390 13.430 115 7.2 9 19.03 85.21 165.2 426.13 11.590 30.62 44.59013.200 115 7.6 Example 2 1 7.54 82.59 159.4 361.70 7.460 29.31 52.81010.420 115 1.5 2 7.67 82.99 160.4 361.70 7.460 29.31 52.810 10.420 1151.8 3 7.79 83.77 159.8 361.70 7.460 29.31 52.810 10.420 115 2.0 4 7.9684.20 160.0 361.70 7.460 29.31 52.810 10.420 115 2.3 5 7.97 84.28 159.6361.70 7.460 29.31 52.810 10.420 115 2.6 6 8.05 84.43 159.6 361.70 7.46029.31 52.810 10.420 115 3.0 7 4.32 88.03 154.4 365.00 7.370 29.97 52.33010.330 115 4.4 8 4.82 85.51 160.4 365.00 7.370 29.97 52.330 10.330 1155.4 9 4.88 85.55 160.9 365.00 7.370 29.97 52.330 10.330 115 5.8 10 4.9385.61 160.9 365.00 7.370 29.97 52.330 10.330 115 6.1 11 6.19 86.15 159.1365.00 7.370 29.97 52.330 10.330 115 8.3 12 6.17 86.03 159.1 365.007.370 29.97 52.330 10.330 115 8.7 13 6.18 85.97 159.1 365.00 7.370 29.9752.330 10.330 115 9.1 14 6.39 84.54 161.0 365.00 7.370 29.97 52.33010.330 115 9.5 15 6.54 85.10 161.0 365.00 7.370 29.97 52.330 10.330 1159.8 16 6.66 85.40 161.0 365.00 7.370 29.97 52.330 10.330 115 10.2Example 3 1 8.83 84.17 160.0 362.80 7.610 29.36 52.650 10.390 115 1.7 28.81 84.65 159.0 362.80 7.610 29.36 52.650 10.390 115 2.5 3 8.68 85.17159.0 362.80 7.610 29.36 52.650 10.390 115 3.6 4 8.64 85.30 159.0 362.807.610 29.36 52.650 10.390 115 4.1 Example 4 1 11.48 88.68 162.0 396.417.040 30.65 47.930 14.380 115 3.7 2 11.49 87.63 162.0 396.41 7.040 30.6547.930 14.380 115 4.1 3 12.46 87.24 164.0 396.41 7.040 30.65 47.93014.380 115 4.5 4 12.76 86.06 165.0 396.41 7.040 30.65 47.930 14.380 1154.9 Example 5 1 7.64 87.33 158.7 396.41 7.040 30.65 47.930 14.380 1150.5 2 9.17 87.84 161.0 396.41 7.040 30.65 47.930 14.380 115 0.9 3 8.6489.49 157.0 396.41 7.040 30.65 47.930 14.380 115 1.3 Example 6 1 9.8984.22 161.3 363.60 7.450 29.65 52.530 10.369 115 5.1 2 10.45 83.70 163.1363.60 7.450 29.65 52.530 10.369 115 5.6 3 10.14 85.54 160.0 363.607.450 29.65 52.530 10.369 115 6.1 4 10.17 85.65 159.2 363.60 7.450 29.6552.530 10.369 115 6.6 5 14.53 85.18 161.0 382.60 10.795 24.49 49.92214.794 115 10.3 6 14.84 85.46 160.0 382.60 10.795 24.49 49.922 14.794115 10.8 7 15.30 85.84 159.6 382.60 10.795 24.49 49.922 14.794 115 11.28 17.23 87.88 159.6 382.60 10.795 24.49 49.922 14.794 115 11.7 9 15.5285.98 159.6 382.60 10.795 24.49 49.922 14.794 115 12.2 Example 7 1 9.3878.05 162.7 363.90 7.610 29.60 51.940 10.850 115 0.8 2 9.74 80.27 160.8363.90 7.610 29.60 51.940 10.850 115 1.6 3 9.77 80.97 160.6 363.90 7.61029.60 51.940 10.850 115 2.6 4 9.62 81.73 160.6 363.90 7.610 29.60 51.94010.850 115 3.6 5 9.67 82.93 159.8 363.90 7.610 29.60 51.940 10.850 1154.5 Example 8 1 10.61 85.55 161.0 362.30 7.730 29.70 52.170 10.410 1152.0 2 9.83 85.42 161.0 362.30 7.730 29.70 52.170 10.410 115 4.0 Example9 1 14.75 88.30 158.0 408.20 7.450 31.97 46.790 13.790 115 2.2 2 14.7088.90 157.0 408.20 7.450 31.97 46.790 13.790 115 2.6 3 14.69 89.60 157.0408.20 7.450 31.97 46.790 13.790 115 2.9 4 14.44 89.90 157.0 408.207.450 31.97 46.790 13.790 115 3.3 5 16.63 88.30 158.0 414.90 8.940 31.4546.040 13.570 115 3.8 6 17.15 88.50 158.0 414.90 8.940 31.45 46.04013.570 115 4.1 7 16.93 89.20 158.0 414.90 8.940 31.45 46.040 13.570 1154.5 8 16.09 89.30 157.0 414.90 8.940 31.45 46.040 13.570 115 4.8 9 16.9488.20 160.0 414.90 8.940 31.45 46.040 13.570 115 5.2 10 17.14 88.40160.0 414.90 8.940 31.45 46.040 13.570 115 5.6 11 16.87 89.10 160.0414.90 8.940 31.45 46.040 13.570 115 5.9 12 16.54 89.20 160.0 414.908.940 31.45 46.040 13.570 115 6.3 13 14.54 88.70 163.0 418.60 9.68031.18 45.630 13.520 115 9.8 14 14.39 88.80 162.0 418.60 9.680 31.1845.630 13.520 115 10.1 15 14.10 89.10 161.0 418.60 9.680 31.18 45.63013.520 115 10.5 16 15.10 88.10 165.0 418.60 9.680 31.18 45.630 13.520115 10.8 17 15.13 87.60 165.0 418.60 9.680 31.18 45.630 13.520 115 11.218 15.71 87.60 168.0 418.60 9.680 31.18 45.630 13.520 115 11.5 19 15.1987.60 166.0 418.60 9.680 31.18 45.630 13.520 115 11.9 Example 10 1 1.9091.40 154.0 418.30 9.980 31.20 45.660 13.460 115 3.0 2 1.99 90.90 154.0418.30 9.980 31.20 45.660 13.460 115 3.3 3 2.73 88.50 162.0 418.30 9.98031.20 45.660 13.460 115 3.6 4 3.52 87.30 163.0 418.30 9.980 31.20 45.66013.460 115 4.0 5 4.61 86.80 163.0 418.30 9.980 31.20 45.660 13.460 1154.3 6 6.53 82.00 169.0 418.30 9.980 31.20 45.660 13.460 115 4.7 7 7.7580.70 173.0 418.30 9.980 31.20 45.660 13.460 115 5.0 8 8.73 80.60 176.0418.30 9.980 31.20 45.660 13.460 115 5.4 9 8.93 82.10 175.0 418.30 9.98031.20 45.660 13.460 115 5.7 Example 11 1 13.27 86.90 159.0 408.20 7.45031.97 46.790 13.790 115 1.3 2 13.89 87.00 159.0 408.20 7.450 31.9746.790 13.790 115 1.6 3 13.88 87.20 159.0 408.20 7.450 31.97 46.79013.790 115 2.0 4 13.88 87.30 159.0 408.20 7.450 31.97 46.790 13.790 1152.3 5 13.74 87.40 159.0 408.20 7.450 31.97 46.790 13.790 115 2.6 6 15.8285.30 162.0 418.30 9.980 31.20 45.660 13.460 115 3.5 7 15.96 84.80 162.0418.30 9.980 31.20 45.660 13.460 115 3.9 8 15.64 85.30 161.0 418.309.980 31.20 45.660 13.460 115 4.2 9 15.65 85.70 160.0 418.30 9.980 31.2045.660 13.460 115 4.5 10 16.28 84.50 164.0 418.30 9.980 31.20 45.66013.460 115 4.9 11 16.28 84.60 165.0 418.30 9.980 31.20 45.660 13.460 1155.2 12 16.51 84.70 165.0 418.30 9.980 31.20 45.660 13.460 115 5.6 1316.51 84.70 165.0 418.30 9.980 31.20 45.660 13.460 115 5.8 Example 12 113.46 83.11 159.6 407.63 6.750 32.50 46.980 13.770 115 1.4 2 13.88 84.15159.6 407.63 6.750 32.50 46.980 13.770 115 1.8 3 13.85 84.39 159.0407.63 6.750 32.50 46.980 13.770 115 2.2 4 14.01 84.91 159.0 407.636.750 32.50 46.980 13.770 115 2.7 5 13.67 85.31 158.0 407.63 6.750 32.5046.980 13.770 115 3.1 6 13.96 84.51 163.5 421.03 9.710 31.47 45.48013.330 115 4.8 7 13.03 85.43 160.0 421.03 9.710 31.47 45.480 13.330 1155.6 8 12.35 85.95 159.0 421.03 9.710 31.47 45.480 13.330 115 6.5 9 11.9086.00 157.0 421.03 9.710 31.47 45.480 13.330 115 6.9 10 11.54 86.24156.0 421.03 9.710 31.47 45.480 13.330 115 7.3 11 11.41 86.62 156.0421.03 9.710 31.47 45.480 13.330 115 7.8 Example 13 1 8.90 84.34 157.2421.91 9.690 31.40 45.390 13.510 115 0.8 2 8.54 83.98 156.0 421.91 9.69031.40 45.390 13.510 115 1.5 3 8.22 84.26 163.2 421.91 9.690 31.40 45.39013.510 115 2.5 4 7.42 84.87 157.4 421.91 9.690 31.40 45.390 13.510 1153.4 5 6.97 85.27 156.5 421.91 9.690 31.40 45.390 13.510 115 4.2 Example14 1 10.74 81.77 164.4 408.07 6.739 32.47 46.928 13.863 115 0.5 2 9.9884.55 161.1 408.07 6.739 32.47 46.928 13.863 115 0.9 3 9.24 86.01 159.0408.07 6.739 32.47 46.928 13.863 115 1.4 4 10.61 83.39 165.0 421.479.704 31.44 45.436 13.422 115 4.0 5 10.13 83.92 165.8 421.47 9.704 31.4445.436 13.422 115 4.4 6 8.69 86.00 162.0 421.47 9.704 31.44 45.43613.422 115 5.3 Example 15 1 7.45 83.44 159.0 408.07 6.739 32.47 46.92813.863 115 0.9 2 7.47 84.09 158.0 408.07 6.739 32.47 46.928 13.863 1151.3 3 7.15 84.60 158.0 408.07 6.739 32.47 46.928 13.863 115 1.8 4 6.6385.15 157.0 408.07 6.739 32.47 46.928 13.863 115 2.6 5 7.60 82.18 159.0421.47 9.704 31.44 45.436 13.422 115 3.9 6 6.99 82.28 159.0 421.47 9.70431.44 45.436 13.422 115 4.8 7 6.14 83.52 158.0 421.47 9.704 31.44 45.43613.422 115 6.0 Example 16 1 4.78 80.03 155.6 408.51 6.730 32.43 46.88013.960 115 2.5 Example 17 1 11.99 85.37 159.5 408.51 6.730 32.43 46.88013.960 115 1.5 2 11.68 85.86 159.5 408.51 6.730 32.43 46.880 13.960 1151.9 3 11.41 86.28 158.0 408.51 6.730 32.43 46.880 13.960 115 2.3 4 10.9587.07 156.3 408.51 6.730 32.43 46.880 13.960 115 2.7 5 10.29 87.36 156.6408.51 6.730 32.43 46.880 13.960 115 3.2 6 11.38 86.38 157.3 421.919.694 31.41 45.389 13.512 115 3.6 7 11.60 85.38 159.0 421.91 9.694 31.4145.389 13.512 115 4.5 8 11.11 85.98 158.9 421.91 9.694 31.41 45.38913.512 115 5.3 9 10.52 86.48 159.9 421.91 9.694 31.41 45.389 13.512 1156.2 Example 18 1 12.01 80.41 170.0 408.51 6.730 32.43 46.880 13.960 1151.1 2 10.91 85.10 156.7 408.51 6.730 32.43 46.880 13.960 115 1.6 3 12.3984.94 159.0 421.91 9.694 31.41 45.389 13.512 115 2.4 4 10.89 84.98 161.0421.91 9.694 31.41 45.389 13.512 115 3.3 5 11.13 85.42 161.0 421.919.694 31.41 45.389 13.512 115 3.7 6 10.12 86.21 159.0 421.91 9.694 31.4145.389 13.512 115 5.0 7 8.68 88.28 156.0 421.91 9.694 31.41 45.38913.512 115 6.7 8 7.41 89.84 154.7 421.91 9.694 31.41 45.389 13.512 1159.3 Example 19 1 10.66 84.76 162.9 408.51 6.730 32.43 46.880 13.960 1151.4 2 9.34 85.79 158.5 408.51 6.730 32.43 46.880 13.960 115 2.3 3 8.8286.11 158.5 421.91 9.694 31.41 45.389 13.512 115 3.1 4 7.34 87.94 158.5421.91 9.694 31.41 45.389 13.512 115 4.4 Example 20 1 6.06 82.27 156.8408.51 6.730 32.43 46.880 13.960 115 1.4 2 5.66 83.00 156.8 408.51 6.73032.43 46.880 13.960 115 3.1 3 5.11 83.60 156.8 408.51 6.730 32.43 46.88013.960 115 6.1

[0072] Reactor Testing For Examples 21 to 35

[0073] The catalysts were tested in a bench scale fluid bed reactor witha maximum catalyst capacity of 40 cm³. 30 cm³ of catalyst orcatalyst-plus-diluent was the volume of solid loaded into the reactorfor each experiment. For some of the experiments, the total of 30 cm³reactor volume was obtained by mixing sufficient microspheroidal silicadiluent (loaded with Au and KOAc only) with the active catalyst prior toreactor testing. The reactor was equipped with two feed inlets. For someof the experiments of this study, ethylene, acetic acid, and oxygen allentered the reactor through the lower inlet and nitrogen only was fedthrough the central inlet. In other tests, additional oxygen was fedthrough the central feed inlet. This central inlet was located 2.5inches above the lower feed inlet.

[0074] The reactor pressure was controlled at 115 psig and all linesleading to and from the reactor were heat traced and maintained at 150°to 160° C. in order to prevent condensation of liquid feeds or products.Typical temperatures for the fluid bed reactor can vary between 1000 to250° C., preferably 135° to 190° C.

[0075] The gaseous reactor effluent was analysed on-line using a HewlettPackard Model 5890 gas chromatograph equipped with both TCD and FIDdetectors. Oxygen, nitrogen, ethylene and carbon dioxide were separatedon a 13x mole sieve column parallel with 10% Carbowax 20M on 80/100Chromosorb WAW and 23% SP2700 on 80/100 Chromosorb PAW, and quantifiedwith the TCD. Vinyl acetate and acetic acid and other organicby-products were separated on a J&W DB1701 megabore capillary column andquantified with the FID. Data was analyzed via a customized Excelspreadsheet.

[0076] Support Preparation

[0077] The support used for all catalyst preparations was prepared byspray drying a mixture of Nalco (Nalco Chemical Co) silica sol 1060 andDeGussa Aerosil® (DeGussa Chemical Company) silica. In the driedsupport, 80% of the silica came from the sol and 20% of the silica camefrom a silica source such as Aerosil®. The spray dried microspheres werecalcined in air at 640° C. for 4 hours. It should be understood that thesupport preparation given above is not intended to be restricted to thistype of silica sol or to this particular silica.

[0078] Prior to use, the support was sieved to remove particles ofdiameter greater than 105 microns. The particle size distribution of theresulting support was used in all catalyst preparations: Particle Size %90-105 microns 18.5 45-90 microns 56.1 <45 microns 25.4

[0079] It should be understood that the particle size distributionrecited above is not intended to be limiting and that variations in thisdistribution are contemplated depending upon reactor size and operatingconditions.

[0080] Catalyst Preparation

[0081] The following procedures describe the method of preparation of afluid bed vinyl acetate catalyst with a metals loading of 0.42 wt % Pd,0.21 wt % Au and 7.0 wt % KOAc. Catalysts with different Pd and Auloadings were prepared by simply scaling the amounts of Na₂PdCl₄.xH₂Oand HAuCl₄.xH₂O used in the preparation. (It should be noted thatalternative water-soluble sources of Pd and Au could be used in place ofNa₂PdCl₄.xH₂O and HAuCl₄.xH₂O.)

[0082] Catalyst Preparation—Standard Procedure A

[0083] Stage 1 Pd, Au Impregnation (Non-Sequential)

[0084] 30.0 g of microspheroidal silica support was impregnated with asolution of Na₂PdCl₄.xH₂O (0.4747 g, 28.9% Pd) and HAuCl₄.xH₂O (0.1370g, 49.0% Au) in distilled H₂O (30.0 cm³) by incipient wetness. Theresulting mixture was mixed thoroughly and then left to stand for 1hour. After this time the mixture was dried overnight at 60° C.

[0085] Stage 2 Reduction and Washing

[0086] The impregnated, dried silica (from stage 1) was allowed to coolto room temperature, and then a solution of hydrazine (3.0 g of a 55%aqueous solution of N₂H₄) in 80.0 cm³ distilled H₂O was added slowly,and the mixture allowed to stand for 3 hours with occasional stirring.After this time, the mixture was filtered and washed with 4×250 cm³distilled H₂O, and then air-dried at room temperature. The solid wasthen dried overnight at 60° C.

[0087] Stage 3 KOAc Treatment

[0088] The treated silica (from stage 2) was then impregnated with asolution of KOAc in distilled H₂O (30.0 cm³) by incipient wetness. Theamount of KOAc used was sufficient to give a final loading of 7 wt %KOAc on the silica (ie 2.258 g KOAc required for 30 g treated silica).The resulting mixture was mixed thoroughly and then left to stand for 1hour. After this time the mixture was dried overnight at 60° C.

[0089] Catalyst Preparation—Standard Procedure B

[0090] Stage 1 Pd, Au Impregnation (Sequential)

[0091] 30.0 g of microspheroidal silica support was impregnated with asolution of Na₂PdCl₄.xH₂O (0.4747 g, 28.9% Pd) in distilled H₂O (30.0cm³) by incipient wetness. The resulting mixture was mixed thoroughlyand then left to stand for 1 hour. After this time the mixture was driedovernight at 60° C. The impregnated, dried silica was then impregnatedwith a solution of HAuCl₄.xH₂O (0.1370 g, 49.0% Au) by incipientwetness. The resulting mixture was mixed thoroughly and then left tostand for 1 hour. After this time the mixture was dried overnight 60° C.

[0092] Stages 2 and 3

[0093] As for Standard Procedure A.

EXAMPLE 21 to 35

[0094] Catalysts prepared by the above method were tested for theacetoxylation of ethylene and the results are collated in Tables 3 to 5.For Examples 21 to 29 (Tables 3 and 4), oxygen conversion was maintainedat a constant level (approx. 30%) and Au/K loaded diluent was used withthe active catalyst; this enabled catalysts of high activity to betested. Examples 21 to 25 (Table 3) demonstrate that as metals loadingsare increased, catalyst activity increases. For Examples 21 to 25, theAu/Pd ratio is a constant (Au/Pd=0.5).

[0095] Examples 26 to 28 (Table 4) show the effect of use of a higherAu/Pd ratio (Au/Pd=2.0). Activity per g of Pd is higher for thesecatalysts compared to those at the lower Au/Pd ratio. Selectivity to VAis also higher at the higher Au/Pd ratio.

[0096] Example 29 (Table 4) demonstrates that the Au/K diluent is inert.

[0097] For Examples 30 to 35 (Table 5), the reactor was filled withcatalyst (i.e. no diluent was used), and oxygen conversion was allowedto vary. The purpose of these examples is to demonstrate high ethyleneconversion. Au/Pd ratios of 0.5, 1.0, 1.3, 1.9 and 2.0 were employed.Example 35, where the Au/Pd ratio is 1.9, shows both high ethyleneconversion (up to 19.4%) and high selectivity (up to 90.8%). TABLE 3 Wt% Wt % Wt. of Wt. of Bed Bath % O₂ % C₂H₄ % VA gVA/ gVA/ Time onExample^(a) Run # Pd^(b) Au^(b) Cat./g Pd^(b)/g temp. temp. Conv. Conv.Selectivity gPd/h kg-cat/h stream/h 21 17551 0.42 0.21 7.00 0.0296 152148 32.9 6.2 85.8 70.6 299 0.5 −21 152 147 32.0 6.3 86.1 72.5 306 1.5152 147 32.0 6.2 87.5 72.6 308 2.5 153 147 32.8 6.9 85.5 79.3 335 3.5153 147 33.5 6.9 87.9 81.3 344 4.3 22 17551 0.64 0.31 5.10 0.0324 153147 32.3 7.3 88.7 78.4 498 0.7 −66^(c) 153 147 32.7 7.5 89.1 81.5 5181.5 152 146 33.5 7.7 88.4 83.1 529 2.5 153 146 34.6 7.9 89.0 85.6 5453.5 152 146 34.4 8.0 89.8 87.6 558 4.3 23 17551 0.85 0.42 3.40 0.0288153 148 29.1 6.5 88.1 78.4 663 0.5 −27 152 147 28.9 7.0 87.0 82.5 6981.5 152 147 31.6 7.1 88.4 86.1 729 2.5 152 147 30.9 7.4 87.0 87.3 7383.5 152 147 32.1 7.3 89.0 88.5 749 4.3 24 17551 1.05 0.52 2.95 0.0312153 147 33.5 7.4 88.9 82.8 876 0.7 −62 153 147 34.4 7.8 87.8 86.3 9141.7 152 146 34.6 7.9 90.0 89.5 948 2.5 152 146 35.2 8.0 89.6 90.0 9533.5 152 146 34.7 7.9 90.2 89.5 948 4.3 25 17551 1.27 0.62 2.26 0.0287152 150 16.7 3.7 83.1 42.1 534 0.5 −32 153 149 22.8 4.9 85.7 57.7 7331.5 152 148 26.0 5.6 85.9 65.5 831 2.5 153 148 28.2 5.9 83.9 67.7 8593.5 152 147 28.4 5.8 87.3 69.4 880 4.5

[0098] TABLE 4 Wt % Wt % Wt. of Wt. of Pd Bed Bath % O₂ % C₂H₄ % VA gVA/gVA/kg- Time on Example^(a) Run # Pd^(b) Au^(b) Cat./g ^(b)/g temp.temp. Conv. Conv. Selectivity gPd/h cat/h stream/h 26 17551 0.42 0.835.45 0.0231 152 150 24.0 5.9 88.6 88.8 376 0.5 −41^(c) 153 149 27.5 7.090.8 107.7 456 1.5 152 148 29.2 7.3 90.3 112.2 475 2.5 153 148 31.2 7.692.3 119.9 508 3.5 153 148 31.6 7.9 91.6 122.9 521 4.3 27 17551 0.641.25 4.27 0.0272 153 147 31.8 7.3 90.0 96.5 614 0.5 −57 153 147 32.5 7.791.2 102.7 653 1.5 153 146 32.8 7.8 91.9 105.0 668 2.5 152 146 33.0 7.890.8 103.3 657 3.5 152 146 33.3 8.0 91.0 107.0 681 4.3 28 17551 0.851.66 3.77 0.0319 152 146 34.0 7.9 90.2 89.5 758 0.5 −53 153 146 35.8 8.392.0 95.3 807 1.5 153 146 37.6 9.2 89.7 103.2 875 2.5 153 145 36.3 8.891.2 100.2 849 3.5 152 145 33.3 8.7 91.1 99.4 842 4.3 29 17551 0 0 0 0151 150 1.1 0.5 — — — 0.5 −71 (diluent 150 149 −0.8 0.5 — — — 1.5 only)150 150 −0.1 0.6 — — — 2.5 150 149 0.7 0.6 — — — 3.5

[0099] TABLE 5 Time on Wt % Wt % Wt. of Wt. of Bed Bath % O₂ % AcOH % O₂% C₂H₄ % VA gVA/ gVA/kg- stream/ Example^(a) Run # Pd^(b) Au^(b) Cat./gPd^(b)/g temp. temp. fed fed Conv. Conv. Selectivity gPd/h cat/h h 3017513 0.22 0.11 21.91 0.0464 154 150 7.6 10.1 21.3 5.1 84.3 36.1 77 0.5−61^(c) 156 150 7.6 10.1 26.0 6.0 83.4 42.3 90 1.5 154 147 7.6 10.1 27.06.2 86.5 45.3 96 2.7 158 149 7.6 10.1 32.5 6.9 85.0 49.6 105 3.6 159 1507.6 10.1 36.3 7.4 85.1 53.5 113 4.5 31 17513 0.42 0.21 22.03 0.0932 152138 7.6 10.1 65.0 12.5 87.3 46.5 197 0.5 −40^(c) 153 138 9.1 11.9 57.413.1 87.2 48.3 204 1.5 155 140 9.1 11.9 57.7 14.5 87.8 54.0 229 3.2 159141 10.5 14.1 58.2 15.6 86.4 57.1 242 4.2 162 143 10.5 14.1 58.6 16.085.4 57.8 245 4.9 32 17513 0.42 0.43 21.87 0.0926 154 135 7.6 10.2 81.014.7 87.8 54.5 231 0.5 −14^(c) 155 135 9.1 12.2 73.5 16.4 87.2 60.3 2561.5 153 135 10.4 14.5 67.2 16.8 87.4 61.9 262 2.5 157 138 10.4 14.5 68.816.6 84.4 58.8 249 3.5 162 140 10.4 14.5 80.2 17.2 83.1 60.1 255 4.4 3317513 0.32 0.43 21.87 0.0695 154 138 7.6 10.2 75.7 15.1 89.2 76.5 2430.5 −56^(c) 154 138 9.1 12.3 65.9 16.0 89.5 81.8 260 1.5 155 138 10.514.2 61.3 17.2 88.0 86.3 274 2.5 157 139 10.5 14.2 65.6 17.3 88.2 86.9276 3.5 34 17513 0.22 0.43 21.88 0.0463 153 144 7.6 10.0 64.5 12.8 90.299.0 210 0.5 −29^(c) 154 144 9.1 12.2 55.8 13.8 90.1 106.3 225 1.5 157146 9.1 12.2 61.1 14.5 89.5 110.9 235 2.5 158 147 10.5 14.0 55.2 14.488.8 109.3 231 3.5 161 149 10.5 14.0 59.5 15.5 87.9 116.7 247 4.4 3517551 0.32 0.62 21.87 0.0692 153 136 7.6 10.2 72.7 14.7 90.0 74.9 2380.5 −03^(c) 153 137 9.1 12.2 65.4 16.3 89.2 82.4 261 1.5 154 137 10.514.2 61.2 19.4 90.8 100.0 318 2.7 152 137 10.5 14.2 58.2 16.8 89.7 85.6272 3.5 156 139 10.5 14.2 51.4 17.7 88.8 89.1 283 4.3

What we claim as our invention is:
 1. A support for the manufacture ofthe vinyl acetate catalyst comprising a mixture of substantially inertmicrospheroidal particles having a pore volume of between 0.2 to 0.7cc/g, a surface area of between 50 to 200 m²/g and at least 50% of saidparticles are less than 105 microns.
 2. The support of claim 1 whereinthe pore volume is between 0.3 and 0.65 cc/g, the surface area isbetween 50 to 150 m²/g and at least 75% of the particles are below 105microns.
 3. The support of claim 2 wherein the substantially inertmicrospheroidal particles are selected from the group consisting ofsilica, zirconia, alumina, titania and mixtures thereof.
 4. The supportof claim 3 wherein the substantially inert microspheroidal particles areselected to be silica.
 5. A process for the manufacture of asubstantially inert support for a fluid bed vinyl acetate catalystcomprising mixing less than 100% to 20 wt % of an aqueous sol comprisingsubstantially inert microspheroidal particles with greater than 0% to 80wt % of solid substantially inert particulate material to form anaqueous mixture, spray drying said aqueous mixture, and calcining saidparticles to form said substantially inert support.
 6. The process ofclaim 5 wherein said substantially inert particles in the aqueous solare selected from the group consisting of silica, alumina, titania andzirconia.
 7. The support made by the process of claim
 5. 8. The supportmade by the process of claim 6 wherein the substantially inert particlesare silica.
 9. A process of manufacturing a fluid bed vinyl acetatecatalyst characterized by the following formula comprising Pd-M-A whereM equals barium, cadmium, gold, lanthanum, niobium, cerium, zinc, lead,calcium, strontium, antimony, or mixtures thereof; and A equals at leastone alkali metal comprising impregnating the support of claim 1 with asolution comprising a metal salt of palladium, M, and at least onealkali metal and drying the impregnated support.
 10. The process ofclaim 9 comprising impregnating the support of claim
 2. 11. The processof claim 9 comprising impregnating the support of claim
 3. 12. Theprocess of claim 9 comprising impregnating the support of claim
 4. 13.The process of claim 9 comprising impregnating the support of claim 7.14. The process of claim 9 comprising impregnating the support of claim8.
 15. The process of claim 9 wherein the support is impregnated with anaqueous solution substantially free of organic solvent comprising ametal salt of Pd, M and at least one alkali metal.
 16. The process ofclaim 10 wherein the support is impregnated with an aqueous solutionsubstantially free of organic solvent comprising a metal salt of Pd, Mand at least one alkali metal.
 17. The process of claim 11 wherein thesupport is impregnated with an aqueous solution substantially free oforganic solvent comprising a metal salt of Pd, M and at least one alkalimetal.
 18. The process of claim 12 wherein the support is impregnatedwith an aqueous solution substantially free of organic solventcomprising a metal salt of Pd, M and at least one alkali metal.
 19. Theprocess of claim 13 wherein the support is impregnated with an aqueoussolution substantially free of organic solvent comprising a metal saltof Pd, M and at least one alkali metal.
 20. The process of claim 14wherein the support is impregnated with an aqueous solutionsubstantially free of organic solvent comprising a metal salt of Pd, Mand at least one alkali metal.
 21. A process for the manufacture ofvinyl acetate comprising contacting the catalyst produced by the processof claim 9 in a fluid bed reactor with a gaseous mixture of acetic acid,ethylene, and an oxygen containing gas to produce vinyl acetate andrecovering the vinyl acetate from the fluid bed reactor.
 22. The processof claim 21 performed at a reaction temperature of 100° to 250° C. 23.The process of claim 22 wherein the reaction temperature is betweenabout 135° to 190° C.
 24. The process of claim 21 performed at areaction pressure of 50 to 200 psig.
 25. The process of claim 24 whereinthe reaction pressure is between about 75 to 150 psig.
 26. A process forthe manufacture of vinyl acetate comprising contacting the catalystproduced by the process of claim 15 in a fluid bed reactor with agaseous mixture of acetic acid, ethylene, and an oxygen containing gasto produce vinyl acetate and recovering the vinyl acetate from the fluidbed reactor.
 27. The process of claim 26 performed at a reactiontemperature of 100° to 250° C.
 28. The process of claim 27 wherein thereaction temperature is between about 135° to 190° C.
 29. The process ofclaim 26 performed at a reaction pressure of 50 to 200 psig.
 30. Theprocess of claim 29 wherein the reaction pressure is between about 75 to150 psig.